82 300td. I changed gasket with one from **************,still leaked Bought a good used valve cover from Mercedes source with the filing on towers done as well as being checked for warping . Got a Mercedes gasket and it still leaks. What to do?Everyoe says no rtv .i ve never used it

Try installing the cover without the gasket and lightly torquing it in place to look for uneven spacing.

Any chance of a restricted breather system causing crankcase pressure or is it a high miler with blowby?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Could be high crankcase pressure. I’ll check hose. Good call

Has anyone used rtv on their valve covers? If so, what kind-brand

I've not used RTV on that cover but if I had to I'd use Permatex "The Right Stuff". Clean and dry every surface with alcohol and let it dry. Apply the sealant as per the instructions and don't start the engine nor add oil for at least 24 hours, 48 is even better.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Is sealant applied to gasket or head?

Using it sparingly, I'd put it in the groove of the gasket, install the gasket on the valve cover, clean away any sealant that squeezes out and then put it again sparingly, on the gasket area that contacts the head. Let it dry for a couple of days if possible before using it but not less than 24 hours.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

When you say cure, do you mean putting on gasket and waiting 24 hours before installing vc to head?

Follow the instructions on the tube as some differ slightly, some want it hand tightened only at first and then after one hour torqued to spec. By cure I mean installed, torqued and left to sit/cure. Don't even add oil until it is completely cured because as you can probably visualize any oil added could flood the gasket until it drained down to the pan.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thank you for all the info

You are welcome, please post the outcome.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Light coat on gasket all the way around- right stuff black. No leak but on start up lots of blue smoke. Is it possible with vc now tight less crankcase pressure can leak out producing smoke? I haven’t driven yet, had to fix something else

Possible yes, likely no. That same pressure can be relieved by lifting the dipstick. Look for a restricted breather.

How many miles? Is the smoke new?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Smoke new, 221k. I’ll get to drive it in a few days and evaluate

The only breather I know of is on top of vc to air cleaner. I haven’t driven yet left that disconnected, no hose to air cleaner. What other breather is there